This invention relates to the use of a fragmentable electron donor with core/shell, light-sensitive, silver halide emulsions.
Core/shell bromoiodide emulsions containing high iodide regions have long been a staple of the blue-sensitive layer in color film. Their intrinsic light absorption in the blue region together with their low response to pressure, continue to make them an attractive choice, especially as the fast component. Recent techniques have been developed to improve the photographic performance of such emulsions by introducing twin planes (Maternaghan in U.S. Pat. No. 4,184,877), producing grains with a particular iodide architecture (Takada et al in U.S. Pat. No. 4,668,614, Ishikawa et al in U.S. Pat. No. 4,963,467), narrowing the range of iodide in individual grains (Shibahara et al in U.S. Pat. No. 4,728,602), and growing grains free of renucleation while obtaining a narrow distribution of grains with a high iodide content (Chang et al, U.S. Pat. No. 5,570,327). All of these methods suffer, however, from various disadvantages such as requiring a seed emulsion which has been previously prepared, producing a small yield of emulsion, or requiring excessive growth times. Furthermore, many of these emulsions derive increased photographic response from a narrow size distribution of grains which inherently leads to less latitude in response to light.
There is, thus, a need for a readily prepared, high-iodide, core/shell emulsion of increased photographic response.
One aspect of this invention comprises a silver halide photographic element comprising at least one silver halide emulsion layer comprising core/shell silver halide grains wherein the core region comprises silver bromide with from about 5 to about 20% silver iodide and the shell region comprises silver bromide with about 0.1 to about 10% silver iodide and said layer contains a fragmentable electron donor compound of the formula Xxe2x80x94Yxe2x80x2 or a compound which contains a moiety of the formula xe2x80x94Xxe2x80x94Yxe2x80x2;
wherein
X is an electron donor moiety, Yxe2x80x2 is a leaving proton H or a leaving group Y, with the proviso that if Yxe2x80x2 is a proton, a base, xcex2xe2x88x92, is covalently linked directly or indirectly to X, and wherein:
1) Xxe2x80x94Yxe2x80x2 has an oxidation potential between 0 and about 1.4 V; and
2) the oxidized form of Xxe2x80x94Yxe2x80x2 undergoes a bond cleavage reaction to give the radical Xxe2x80xa2 and the leaving fragment Yxe2x80x2; and, optionally,
3) the radical Xxe2x80xa2 has an oxidation potentialxe2x89xa6xe2x88x920.7V (that is, equal to or more negative than about xe2x88x920.7V).
This invention provides a photographic element comprising a silver halide emulsion having a high intrinsic light absorption in the blue region with a low sensitivity to pressure and an increased photographic response. Further, the emulsion can be readily prepared without a seed emulsion and can be produced in high yield in a short time.
All percentages specified herein are mole %, unless indicated to the contrary.
This invention also provides a high-iodide emulsion with increased photographic response which is especially useful in the blue record of color film. The enhanced speed of the emulsion induced by the fragmentable electron donor allows the use of an emulsion which is readily formed in good yield in a short run time without the need of nucleating seeds. Because the emulsion is, polydisperse it has a wide latitude allowing lower silver coverages in color film.
Useful emulsions in this application include bromide emulsions with core regions containing from 5-20% iodide. Especially useful are those emulsions with cores of from 8-18% iodide. The core is suitably 20-60% of the total grain volume. Especially useful are those with a core of 30-50%. The shell region can be 0-10% iodide but in all cases, the iodide in the shell is less than that in the core. Especially useful are emulsions with a shell comprising from 2-8% iodide. The total iodide of the emulsion can range from 2-15%. Iodide analysis can be performed using X-ray powder diffraction as described by Blanton in Industrial Applications of X-Ray Diffraction, Chapter 25, 1999.
Bromoiodide emulsions have been the mainstay of photographic films for many years. Illingsworth in U.S. Pat. No. 3,320,069 disclosed the utility of bromoiodide emulsions prepared in the presence of thiocyanate. The preferred embodiment is based on such an emulsion although the manner of thiocyanate addition is not critical and, in the present invention, the iodide architecture has been refined.
In the following discussion of silver halide emulsions and their preparation, reference will be made to Research Disclosure, September 1996, Number 389, Item 38957, which will be identified hereafter by the term xe2x80x9cResearch Disclosure I.xe2x80x9d This and all other Research Disclosures referenced herein are published by Kenneth Mason Publications, Ltd., Dudley Annex, 12a North Street, Emsworth, Hampshire P010 7DQ, ENGLAND. The Sections hereafter referred to are Sections of the Research Disclosure I unless otherwise indicated.
The silver halide emulsions employed in the photographic elements of the present invention may be negative-working, such as surface-sensitive emulsions or unfogged internal latent image forming emulsions, or positive working emulsions of the internal latent image forming type (that are fogged during processing). Suitable emulsions and their preparation as well as methods of chemical and spectral sensitization are described in Research Disclosure I, Sections I through V. Color materials and development modifiers are described in Sections V through XX. Vehicles which can be used in the photographic elements are described in Section II, and various additives such as brighteners, antifoggants, stabilizers, light absorbing and scattering materials, hardeners, coating aids, plasticizers, lubricants and matting agents are described, for example, in Sections VI through XIII. Manufacturing methods are described in all of the sections, layer arrangements particularly in Section XI, exposure alternatives in Section XVI, and processing methods and agents in Sections XIX and XX.
With negative working silver halide a negative image can be formed. Optionally a positive (or reversal) image can be formed although a negative image is typically first formed.
The grain size of the core/shell silver halide may have any distribution known to be useful in photographic compositions.
The morphology of the core/shell silver halide may be octahedral, cubic, polymorphic, or tabular.
The silver halide grains to be used in the invention may be prepared according to methods known in the art, such as those described in Research Disclosure I and James, The Theory of the Photographic Process. These include methods such as ammoniacal emulsion making, neutral or acidic emulsion making, and others known in the art. These methods generally involve mixing a water soluble silver salt with a water soluble halide salt in the presence of a protective colloid, and controlling the temperature, pAg, pH values, etc, at suitable values during formation of the silver halide by precipitation.
In the course of grain precipitation one or more dopants (grain occlusions other than silver and halide) can be introduced to modify grain properties. For example, any of the various conventional dopants disclosed in Research Disclosure I, Section I. Emulsion grains and their preparation, sub-section G. Grain modifying conditions and adjustments, paragraphs (3), (4) and (5), can be present in the emulsions of the invention. In addition it is specifically contemplated to dope the grains with transition metal hexacoordination complexes containing one or more organic ligands, as taught by Olm et al U.S. Pat. No. 5,360,712, the disclosure of which is here incorporated by reference.
It is specifically contemplated to incorporate in the face centered cubic crystal lattice of the grains a dopant capable of increasing imaging speed by forming a shallow electron trap (hereinafter also referred to as a SET) as discussed in Research Discolosure Item 36736 published November 1994, here incorporated by reference.
The SET dopants are effective at any location within the grains. Generally better results are obtained when the SET dopant is incorporated in the exterior 50 percent of the grain, based on silver. An optimum grain region for SET incorporation is that formed by silver ranging from 50 to 85 percent of total silver forming the grains. The SET can be introduced all at once or run into the reaction vessel over a period of time while grain precipitation is continuing. Generally SET forming dopants are contemplated to be incorporated in concentrations of at least 1xc3x9710xe2x88x927 mole per silver mole up to their solubility limit, typically up to about 5xc3x9710xe2x88x924 mole per silver mole.
SET dopants are known to be effective to reduce reciprocity failure. In particular the use of iridium hexacoordination complexes or Ir+4 complexes as SET dopants is advantageous.
Iridium dopants that are ineffective to provide shallow electron traps (non-SET dopants) can also be incorporated into the grains of the silver halide grain emulsions to reduce reciprocity failure. To be effective for reciprocity improvement the Ir can be present at any location within the grain structure. A preferred location within the grain structure for Ir dopants to produce reciprocity improvement is in the region of the grains formed after the first 60
The silver halide to be used in the invention may be advantageously subjected to chemical sensitization. Compounds and techniques useful for chemical sensitization of silver halide are known in the art and described in Research Disclosure I and the references cited therein. Compounds useful as chemical sensitizers, include, for example, active gelatin, sulfur, selenium, tellurium, gold, platinum, palladium, iridium, osmium, rhenium, phosphorous, or combinations thereof. Chemical sensitization is generally carried out at pAg levels of from 5 to 10, pH levels of from 4 to 8, and temperatures of from 30 to 80xc2x0 C., as described in Research Disclosure I, Section IV (pages 510-511) and the references cited therein.
The silver halide may be sensitized by sensitizing dyes by any method known in the art, such as described in Research Disclosure I. The dye may be added to an emulsion of the silver halide grains and a hydrophilic colloid at any time prior to (e.g., during or after chemical sensitization) or simultaneous with the coating of the emulsion on a photographic element. The dyes may, for example, be added as a solution in water or an alcohol. The dye/silver halide emulsion may be mixed with a dispersion of color image-forming coupler immediately before coating or in advance of coating (for example, 2 hours).
In accordance with this invention the silver halide emulsion contains a fragmentable electron donating (FED) compound which enhances the sensitivity of the emulsion. The fragmentable electron donating compound is of the formula Xxe2x80x94Yxe2x80x2 or a compound which contains a moiety of the formula xe2x80x94Xxe2x80x94Yxe2x80x2;
wherein
X is an electron donor moiety, Yxe2x80x2 is a leaving proton H or a leaving group Y, with the proviso that if Yxe2x80x2 is a proton, a base, xcex2xe2x88x92, is covalently linked directly or indirectly to X, and wherein:
1) Xxe2x80x94Yxe2x80x2 has an oxidation potential between 0 and about 1.4 V; and percent and before the final 1 percent (most preferably before the final 3 percent) of total silver forming the grains has been precipitated. The dopant can be introduced all at once or run into the reaction vessel over a period of time while grain precipitation is continuing. Generally reciprocity improving non-SET Ir dopants are contemplated to be incorporated at their lowest effective concentrations.
Although generally preferred concentration ranges for the various SET, and non-SET Ir dopants have been set out above, it is recognized that specific optimum concentration ranges within these general ranges can be identified for specific applications by routine testing. It is specifically contemplated to employ the SET and non-SET Ir dopants singly or in combination. For example, grains containing a combination of an SET dopant and a non-SET Ir dopant are specifically contemplated. The photographic elements of the present invention, as is typical, provide the silver halide in the form of an emulsion. Photographic emulsions generally include a vehicle for coating the emulsion as a layer of a photographic element. Useful vehicles include both naturally occurring substances such as proteins, protein derivatives, cellulose derivatives (e.g., cellulose esters), gelatin (e.g., alkali-treated gelatin such as cattle bone or hide gelatin, or acid treated gelatin such as pigskin gelatin), deionized gelatin, gelatin derivatives (e.g., acetylated gelatin, phthalated gelatin, and the like), and others as described in Research Disclosure I. Also useful as vehicles or vehicle extenders are hydrophilic water-permeable colloids. These include synthetic polymeric peptizers, carriers, and/or binders such as poly(vinyl alcohol), poly(vinyl lactams), acrylamide polymers, polyvinyl acetals, polymers of alkyl and sulfoalkyl acrylates and methacrylates, hydrolyzed polyvinyl acetates, polyamides, polyvinyl pyridine, methacrylamide copolymers, and the like, as described in Research Disclosure I. The vehicle can be present in the emulsion in any amount useful in photographic emulsions. The emulsion can also include any of the addenda known to be useful in photographic emulsions.
2) the oxidized form of Xxe2x80x94Yxe2x80x2 undergoes a bond cleavage reaction to give the radical Xxe2x80xa2 and the leaving fragment Yxe2x80x2; and, optionally,
3) the radical Xxe2x80xa2 has an oxidation potentialxe2x89xa6xe2x88x920.7V (that is, equal to or more negative than about xe2x88x920.7V).
Compounds wherein Xxe2x80x94Yxe2x80x2 meets criteria (1) and (2) but not (3) are capable of donating one electron and are referred to herein as fragmentable one-electron donating compounds. Compounds which meet all three criteria are capable of donating two electrons and are referred to herein as fragmentable two-electron donating compounds.
In this patent application, oxidation potentials are reported as xe2x80x9cVxe2x80x9d which represents xe2x80x9cvolts versus a saturated calomel reference electrodexe2x80x9d.
In embodiments of the invention in which Yxe2x80x2 is Y, the following represents the reactions that are believed to take place when Xxe2x80x94Y undergoes oxidation and fragmentation to produce a radical Xxe2x80xa2, which in a preferred embodiment undergoes further oxidation. 
where E1 is the oxidation potential of Xxe2x80x94Y and E2 is the oxidation potential of the radical Xxe2x80xa2.
E1 is preferably no higher than about 1.4 V and preferably less than about 1.0 V. The oxidation potential is preferably greater than 0, more preferably greater than about 0.3 V. E1 is preferably in the range of about 0 to about 1.4 V, and more preferably from about 0.3 V to about 1.0 V.
In certain embodiments of the invention the oxidation potential, E2, of the radical Xxe2x80xa2 is equal to or more negative than xe2x88x920.7V, preferably more negative than about xe2x88x920.9 V. E2 is preferably in the range of from about xe2x88x920.7 to about xe2x88x922 V, more preferably from about xe2x88x920.8 to about xe2x88x922 V and most preferably from about xe2x88x920.9 to about xe2x88x921.6 V.
The structural features of Xxe2x80x94Y are defined by the characteristics of the two parts, namely the fragment X and the fragment Y. The structural features of the fragment X determine the oxidation potential of the Xxe2x80x94Y molecule and that of the radical Xxe2x80xa2, whereas both the X and Y fragments affect the fragmentation rate of the oxidized molecule Xxe2x80x94Yxe2x80xa2+.
In embodiments of the invention in which Yxe2x80x2 is H, the following represents the reactions believed to take place when the compound Xxe2x80x94H undergoes oxidation and deprotonation to the base, xcex2xe2x88x92, to produce a radical Xxe2x80xa2, which in a preferred embodiment undergoes further oxidation. 
Preferred X groups are of the general formula: 
The symbol xe2x80x9cRxe2x80x9d (that is R without a subscript) is used in all structural formulae in this patent application to represent a hydrogen atom or an unsubstituted or substituted alkyl group.
In structure (I):
m=0, 1;
Z=O, S, Se, Te;
Ar=aryl group (e.g., phenyl, naphthyl, phenanthryl, anthryl); or heterocyclic group (e.g., pyridine, indole, benzimidazole, thiazole, benzothiazole, thiadiazole, etc.);
R1=R, carboxyl, amide, sulfonamide, halogen, NR2, (OH)n, (ORxe2x80x2)n, or (SR)n;
Rxe2x80x2=alkyl or substituted alkyl;
n=1-3;
R2=R, Arxe2x80x2;
R3=R, Arxe2x80x2;
R2 and R3 together can form 5- to 8-membered ring;
R2 and Ar=can be linked to form 5- to 8-membered ring;
R3 and Ar=can be linked to form 5- to 8-membered ring;
Arxe2x80x2=aryl group such as phenyl, substituted phenyl, or heterocyclic group (e.g., pyridine, benzothiazole, etc.)
R=a hydrogen atom or an unsubstituted or substituted alkyl group.
In structure (II):
Ar=aryl group (e.g., phenyl, naphthyl, phenanthryl); or heterocyclic group (e.g., pyridine, benzothiazole, etc.);
R4=a substituent having a Hammett sigma value of xe2x88x921 to +1, preferably xe2x88x920.7 to +0.7, e.g., R, OR, SR, halogen, CHO, C(O)R, COOR, CONR2, SO3R, SO2NR2, SO2R, SOR, C(S)R, etc;
R5=R, Arxe2x80x2
R6 and R7=R, Arxe2x80x2
R5 and Ar=can be linked to form 5- to 8-membered ring;
R6 and Ar=can be linked to form 5- to 8-membered ring (in which case, R6 can be a hetero atom);
R5 and R6 can be linked to form 5- to 8-membered ring;
R6 and R7 can be linked to form 5- to 8-membered ring;
Arxe2x80x2=aryl group such as phenyl, substituted phenyl, heterocyclic group;
R=hydrogen atom or an unsubstituted or substituted alkyl group.
A discussion on Hammett sigma values can be found in C. Hansch and R. W. Taft Chem. Rev. Vol 91, (1991) p 165, the disclosure of which is incorporated herein by reference.
In structure (III):
W=O, S, Se;
Ar=aryl group (e.g., phenyl, naphthyl, phenanthryl, anthryl); or heterocyclic group (e.g., indole, benzimidazole, etc.)
R8=R, carboxyl, NR2, (OR)n, or (SR)n (n=1-3);
R9 and R10=R, Arxe2x80x2;
R9 and Ar=can be linked to form 5- to 8-membered ring;
Arxe2x80x2=aryl group such as phenyl substituted phenyl or heterocyclic group;
R=a hydrogen atom or an unsubstituted or substituted alkyl group.
In structure (IV):
xe2x80x9cringxe2x80x9d represents a substituted or unsubstituted 5-, 6- or 7-membered unsaturated ring, preferably a heterocyclic ring.
The following are illustrative examples of the group X of the general structure I: 
In the structures of this patent application a designation such as xe2x80x94OR(NR2) indicates that either xe2x80x94OR or xe2x80x94NR2 can be present.
The following are illustrative examples of the group X of general structure 
Z1=a covalent bond, S, O, Se, NR, CR2, CRxe2x95x90CR, or CH2CH2. 
Z2=S, O, Se, NR, CR2, CRxe2x95x90CR, R13, =alkyl, substituted alkyl or aryl, and R14=H, alkyl substituted alkyl or aryl.
The following are illustrative examples of the group X of the general structure III: 
The following are illustrative examples of the group X of the general structure IV: 
Z3=O, S, Se, NR
R15=R, OR, NR2 
R16=alkyl, substituted alkyl
Preferred Yxe2x80x2 groups are:
(1) Xxe2x80x2, where Xxe2x80x2 is an X group as defined in structures I-IV and may be the same as or different from the X group to which it is attached 
where M=Si, Sn or Ge; and Rxe2x80x2=alkyl or substituted alkyl 
where Arxe2x80x3=aryl or substituted aryl 
In preferred embodiments of this invention Yxe2x80x2 is xe2x80x94H, xe2x80x94COOxe2x80x94 or xe2x80x94Si(Rxe2x80x2)3 or xe2x80x94Xxe2x80x2. Particularly preferred Yxe2x80x2 groups are xe2x80x94H, xe2x80x94COOxe2x80x94 or xe2x80x94Si(Rxe2x80x2)3.
In embodiments of the invention in which Yxe2x80x2 is a proton, a base, xcex2xe2x88x92, is covalently linked directly or indirectly to X. The base is preferably the conjugate base of an acid of pKa between about1 and about 8, preferably about 2 to about 7. Collections of pKa values are available (see, for example: Dissociation Constants of Organic Bases in Aqueous Solution, D. D. Perrin (Butterworths, London, 1965); CRC Handbook of Chemistry and Physics, 77th ed, D. R. Lide (CRC Press, Boca Raton, Fla., 1996)). Examples of useful bases are included in Table I.
Preferably the base, xcex2xe2x88x92 is a carboxylate, sulfate or amine oxide.
In some embodiments of the invention, the fragmentable electron donating compound contains a light absorbing group, Z, which is attached directly or indirectly to X, a silver halide absorptive group, A, directly or indirectly attached to X, or a chromophore forming group, Q, which is attached to X. Such fragmentable electron donating compounds are preferably of the following formulae:
Zxe2x80x94(Lxe2x80x94Xxe2x80x94Yxe2x80x2)k
Axe2x80x94(Lxe2x80x94Xxe2x80x94Yxe2x80x2)k
(Axe2x80x94L)kxe2x80x94Xxe2x80x94Yxe2x80x2
Qxe2x80x94Xxe2x80x94Yxe2x80x2
Axe2x80x94(Xxe2x80x94Yxe2x80x2)k
(A)kxe2x80x94Xxe2x80x94Yxe2x80x2
Zxe2x80x94(Xxe2x80x94Yxe2x80x2)k
or
(Z)kxe2x80x94Xxe2x80x94Yxe2x80x2
Z is a light absorbing group;
k is 1 or 2;
A is a silver halide adsorptive group that preferably contains at least one atom of N, S, P, Se, or Te that promotes adsorption to silver halide;
L represents a linking group containing at least one C, N, S, P or O atom; and
Q represents the atoms necessary to form a chromophore comprising an amidinium-ion, a carboxyl-ion or dipolar-amidic chromophoric system when conjugated with Xxe2x80x94Yxe2x80x2.
Z is a light absorbing group including, for example, cyanine dyes, complex cyanine dyes, merocyanine dyes, complex merocyanine dyes, homopolar cyanine dyes, styryl dyes, oxonol dyes, hemioxonol dyes, and hemicyanine dyes.
Preferred Z groups are derived from the following dyes: 
The linking group L may be attached to the dye at one (or more) of the heteroatoms, at one (or more) of the aromatic or heterocyclic rings, or at one (or more) of the atoms of the polymethine chain, at one (or more) of the heteroatoms, at one (or more) of the aromatic or heterocyclic rings, or at one (or more) of the atoms of the polymethine chain. For simplicity, and because of the multiple possible attachment sites, the attachment of the L group is not specifically indicated in the generic structures.
The silver halide adsorptive group A is preferably a silver-ion ligand moiety or a cationic surfactant moiety. In preferred embodiments, A is selected from the group consisting of: i) sulfur acids and their Se and Te analogs, ii) nitrogen acids, iii) thioethers and their Se and Te analogs, iv) phosphines, v) thionamides, selenamides, and telluramides, and vi) carbon acids.
Illustrative A groups include: 
The point of attachment of the linking group L to the silver halide adsorptive group A will vary depending on the structure of the adsorptive group, and may be at one (or more) of the heteroatoms, at one (or more) of the aromatic or heterocyclic rings.
The linkage group represented by L which connects by a covalent bond the light absorbing group Z or the silver halide adsorbing group A to the fragmentable electron donating group XY is preferably an organic linking group containing a least one C, N, S, or O atom. It is also desired that the linking group not be completely aromatic or unsaturated, so that a pi-conjugation system cannot exist between the Z and XY or the A and XY moieties. Preferred examples of the linkage group include, an alkylene group, an arylene group, xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94Cxe2x95x90O, xe2x80x94SO2xe2x80x94, xe2x80x94NHxe2x80x94, xe2x80x94Pxe2x95x90O, and xe2x80x94Nxe2x95x90. Each of these linking components can be optionally substituted and can be used alone or in combination. Examples of preferred combinations of these groups are: 
where c=1-30, and d=1-10
The length of the linkage group can be limited to a single atom or can be much longer, for instance up to 30 atoms in length. A preferred length is from about 2 to 20 atoms, and most preferred is 3 to 10 atoms. Some preferred examples of L can be represented by the general formulae indicated below: 
e and f=1-30, with the proviso that e+fxe2x89xa631
Q represents the atoms necessary to form a chromophore comprising an amidinium-ion, a carboxyl-ion or dipolar-amidic chromophoric system when conjugated with Xxe2x80x94Yxe2x80x2. Preferably the chromophoric system is of the type generally found in cyanine, complex cyanine, hemicyanine, merocyanine, and complex merocyanine dyes as described in F. M. Hamer, The Cyanine Dyes and Related Compounds (Interscience Publishers, New York, 1964).
Illustrative Q groups include: 
Particularly preferred are Q groups of the formula: 
wherein:
X2 is O, S, N, or C(R19)2, where R19 is substituted or unsubstituted alkyl.
each R17 is independently a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, or substituted or unsubstituted aryl group;
a is an integer of 1-4; and
R18 is substituted or unsubstituted alkyl, or substituted or unsubstituted aryl.
Illustrative fragmentable electron donating compounds include: 
The fragmentable electron donors of the present invention can be included in a silver halide emulsion by direct dispersion in the emulsion, or they may be dissolved in a solvent such as water, methanol or ethanol for example, or in a mixture of such solvents, and the resulting solution can be added to the emulsion. The compounds of the present invention may also be added from solutions containing a base and/or surfactants, or may be incorporated into aqueous slurries or gelatin dispersions and then added to the emulsion. The fragmentable electron donor may be used as the sole sensitizer in the emulsion. However, in preferred embodiments of the invention a sensitizing dye is also added to the emulsion. The compounds can be added before, during or after the addition of the sensitizing dye. The amount of electron donor which is employed in this invention may range from as little as 1xc3x9710xe2x88x928 mole per mole of silver in the emulsion to as much as about 0.1 mole per mole of silver, preferably from about 5xc3x9710xe2x88x927 to about 0.05 mole per mole of silver. Where the oxidation potential E1 for the XY moiety of the electron donating sensitizer is a relatively low potential, it is more active, and relatively less agent need be employed. Conversely, where the oxidation potential for the XY moiety of the electron donating sensitizer is relatively high, a larger amount thereof, per mole of silver, is employed. In addition, for XY moieties that have silver halide adsorptive groups A or light absorptive groups Z or chromophoric groups Q directly or indirectly attached to X, the fragmentable electron donating sensitizer is more closely associated with the silver halide grain and relatively less agent need be employed. For fragmentable one-electron donors relatively larger amounts per mole of silver are also employed. Although it is preferred that the fragmentable electron donor be added to the silver halide emulsion prior to manufacture of the coating, in certain instances, the electron donor can also be incorporated into the emulsion after exposure by way of a pre-developer bath or by way of the developer bath itself.
Fragmentable electron donating compounds are described more fully in U.S. Pat. Nos. 5,747,235 and 5,747,236 and commonly assigned co-pending U.S. application Ser. No. 08/739,911 filed Oct. 30, 1996, and Ser. Nos. 09/118,536, 09/118,552 and 09/118,714 filed Jul. 25, 1998, the entire disclosures of these patents and patent applications are incorporated herein by reference.
The emulsion layer of the photographic element of the invention can comprise any one or more of the light sensitive layers of the photographic element. The photographic elements made in accordance with the present invention can be black and white elements, single color elements or multicolor elements. Multicolor elements contain dye image-forming units sensitive to each of the three primary regions of the spectrum. Each unit can be comprised of a single emulsion layer or of multiple emulsion layers sensitive to a given region of the spectrum. The layers of the element, including the layers of the image-forming units, can be arranged in various orders as known in the art. In an alternative format, the emulsions sensitive to each of the three primary regions of the spectrum can be disposed as a single segmented layer.
A typical multicolor photographic element comprises a support bearing a cyan dye image-forming unit comprised of at least one red-sensitive silver halide emulsion layer having associated therewith at least one cyan dye-forming coupler, a magenta dye image-forming unit comprising at least one green-sensitive silver halide emulsion layer having associated therewith at least one magenta dye-forming coupler, and a yellow dye image-forming unit comprising at least one blue-sensitive silver halide emulsion layer having associated therewith at least one yellow dye-forming coupler. The element can contain additional layers, such as filter layers, interlayers, overcoat layers, subbing layers, and the like. All of these can be coated on a support which can be transparent or reflective (for example, a paper support).
Photographic elements of the present invention may also usefully include a magnetic recording material as described in Research Disclosure, Item 34390, November 1992, or a transparent magnetic recording layer such as a layer containing magnetic particles on the underside of a transparent support as in U.S. Pat. Nos. 4,279,945 and 4,302,523. The element typically will have a total thickness (excluding the support) of from 5 to 30 microns. While the order of the color sensitive layers can be varied, they will normally be red-sensitive, green-sensitive and blue-sensitive, in that order on a transparent support, (that is, blue sensitive furthest from the support) and the reverse order on a reflective support being typical.
The present invention also contemplates the use of photographic elements of the present invention in what are often referred to as single use cameras (or xe2x80x9cfilm with lensxe2x80x9d units). These cameras are sold with film preloaded in them and the entire camera is returned to a processor with the exposed film remaining inside the camera. Such cameras may have glass or plastic lenses through which the photographic element is exposed.
The photographic elements of the present invention may also use colored couplers (e.g. to adjust levels of interlayer correction) and masking couplers such as those described in EP 213 490; Japanese Published Application 58-172,647; U.S. Pat. No. 2,983,608; German Application DE 2,706,117C; U.K. Pat. No. 1,530,272; Japanese Application A-113935; U.S. Pat. No. 4,070,191 and German Application DE 2,643,965. The masking couplers may be shifted or blocked.
The photographic elements may also contain materials that accelerate or otherwise modify the processing steps of bleaching or fixing to improve the quality of the image. Bleach accelerators described in EP 193 389; EP 301 477; U.S. Pat. Nos. 4,163,669; 4,865,956; and 4,923,784 are particularly useful. Also contemplated is the use of nucleating agents, development accelerators or their precursors (UK Patent 2,097,140; U.K. Patent 2,131,188); development inhibitors and their precursors (U.S. Pat. Nos. 5,460,932; 5,478,711); electron transfer agents (U.S. Pat. Nos. 4,859,578; 4,912,025); antifogging and anti color-mixing agents such as derivatives of hydroquinones, aminophenols, amines, gallic acid; catechol; ascorbic acid; hydrazides; sulfonamidophenols; and non color-forming couplers.
The elements may also contain filter dye layers comprising colloidal silver sol or yellow and/or magenta filter dyes and/or antihalation dyes (particularly in an undercoat beneath all light sensitive layers or in the side of the support opposite that on which all light sensitive layers are located) either as oil-in-water dispersions, latex dispersions or as solid particle dispersions. Additionally, they may be used with xe2x80x9csmearingxe2x80x9d couplers (e.g. as described in U.S. Pat. No. 4,366,237; EP 096 570; U.S. Pat. Nos. 4,420,556; and 4,543,323.) Also, the couplers may be blocked or coated in protected form as described, for example, in Japanese Application 61/258,249 or U.S. Pat. No. 5,019,492.
The photographic elements may further contain other image-modifying compounds such as xe2x80x9cDevelopment Inhibitor-Releasingxe2x80x9d compounds (DIR""s). Useful additional DIR""s for elements of the present invention, are known in the art and examples are described in U.S. Pat. Nos. 3,137,578; 3,148,022; 3,148,062; 3,227,554; 3,384,657; 3,379,529; 3,615,506; 3,617,291; 3,620,746; 3,701,783; 3,733,201; 4,049,455; 4,095,984; 4,126,459; 4,149,886; 4,150,228; 4,211,562; 4,248,962; 4,259,437; 4,362,878; 4,409,323; 4,477,563; 4,782,012; 4,962,018; 4,500,634; 4,579,816; 4,607,004; 4,618,571; 4,678,739; 4,746,600; 4,746,601; 4,791,049; 4,857,447; 4,865,959; 4,880,342; 4,886,736; 4,937,179; 4,946,767; 4,948,716; 4,952,485; 4,956,269; 4,959,299; 4,966,835; 4,985,336 as well as in patent publications GB 1,560,240; GB 2,007,662; GB 2,032,914; GB 2,099,167; DE 2,842,063, DE 2,937,127; DE 3,636,824; DE 3,644,416 as well as the following European Patent Publications: 272,573; 335,319; 336,411; 346,899; 362,870; 365,252; 365,346; 373,382; 376,212; 377,463; 378,236; 384,670; 396,486; 401,612; 401,613.
DIR compounds are also disclosed in xe2x80x9cDeveloper-Inhibitor-Releasing (DIR) Couplers for Color Photography,xe2x80x9d C. R. Barr, J. R. Thirtle and P. W. Vittum in Photographic Science and Engineering, Vol. 13, p. 174 (1969), incorporated herein by reference.
It is also contemplated that the concepts of the present invention may be employed to obtain reflection color prints as described in Research Disclosure, November 1979, Item 18716 incorporated herein by reference. The emulsions and materials to form elements of the present invention, may be coated on pH adjusted support as described in U.S. Pat. No. 4,917,994; with epoxy solvents (EP 0 164 961); with additional stabilizers (as described, for example, in U.S. Pat. Nos. 4,346,165; 4,540,653 and 4,906,559); with ballasted chelating agents such as those in U.S. Pat. No. 4,994,359 to reduce sensitivity to polyvalent cations such as calcium; and with stain reducing compounds such as described in U.S. Pat. Nos. 5,068,171 and 5,096,805. Other compounds which may be useful in the elements of the invention are disclosed in Japanese Published Applications 83-09,959; 83-62,586; 90-072,629; 90-072,630; 90-072,632; 90-072,633; 90-072,634; 90-077,822; 90-078,229; 90-078,230; 90-079,336; 90-079,338; 90-079,690; 90-079,691; 90-080,487; 90-080,489; 90-080,490; 90080,491; 90-080,492; 90-080,494; 90-085,928; 90-086,669; 90-086,670; 90-087,361; 90-087,362; 90-087,363; 90-087,364; 90-088,096; 90-088,097; 90-093,662; 90-093,663; 90-093,664; 90-093,665; 90-093,666; 90-093,668; 90-094,055; 90-094,056; 90-101,937; 90-103,409; 90-151,577.
The silver halide may be sensitized by sensitizing dyes by any method known in the art, such as described in Research Disclosure I. The dye may be added to an emulsion of the silver halide grains and a hydrophilic colloid at any time prior to (e.g., during or after chemical sensitization) or simultaneous with the coating of the emulsion on a photographic element. The dyes may, for example, be added as a solution in water or an alcohol. The dye/silver halide emulsion may be mixed with a dispersion of color image-forming coupler immediately before coating or in advance of coating (for example, 2 hours).
Photographic elements of the present invention are preferably imagewise exposed using any of the known techniques, including those described in Research Disclosure I, section XVI. This typically involves exposure to light in the visible region of the spectrum, and typically such exposure is of a live image through a lens, although exposure can also be exposure to a stored image (such as a computer stored image) by means of light emitting devices (such as light emitting diodes, CRT and the like).
Photographic elements comprising the composition of the invention can be processed in any of a number of well-known photographic processes utilizing any of a number of well-known processing compositions, described, for example, in Research Disclosure I, or in T. H. James, editor, The Theory of the Photographic Process, 4th Edition, Macmillan, New York, 1977. In the case of processing a negative working element, the element is treated with a color developer (that is one which will form the colored image dyes with the color couplers), and then with a oxidizer and a solvent to remove silver and silver halide. In the case of processing a reversal color element, the element is first treated with a black and white developer (that is, a developer which does not form colored dyes with the coupler compounds) followed by a treatment to fog silver halide (usually chemical fogging or light fogging), followed by treatment with a color developer. Preferred color developing agents are p-phenylenediamines.
Especially preferred are:
4-amino N,N-diethylaniline hydrochloride,
4-amino-3-methyl-N,N-diethylaniline hydrochloride,
4-amino-3-methyl-N-ethyl-N-(xcex2-(methanesulfonamido)ethylaniline sesquisulfate hydrate,
4-amino-3-methyl-N-ethyl-N-(xcex2-hydroxyethyl)aniline sulfate,
4-amino-3-xcex2-(methanesulfonamido)ethyl-N,N-diethylaniline hydrochloride and
4-amino-N-ethyl-N-(2-methoxyethyl)-m-toluidine di-p-toluene sulfonic acid.
Dye images can be formed or amplified by processes which employ in combination with a dye-image-generating reducing agent an inert transition metal-ion complex oxidizing agent, as illustrated by Bissonette U.S. Pat. Nos. 3,748,138, 3,826,652, 3,862,842 and 3,989,526 and Travis U.S. Pat. No. 3,765,891, and/or a peroxide oxidizing agent as illustrated by Matejec U.S. Pat. No. 3,674,490, Research Disclosure, Vol. 116, December, 1973, Item 11660, and Bissonette Research Disclosure, Vol. 148, August, 1976, Items 14836, 14846 and 14847. The photographic elements can be particularly adapted to form dye images by such processes as illustrated by Dunn et al U.S. Pat. No. 3,822,129, Bissonette U.S. Pat. Nos. 3,834,907 and 3,902,905, Bissonette et al U.S. Pat. No. 3,847,619, Mowrey U.S. Pat. No. 3,904,413, Hirai et al U.S. Pat. No. 4,880,725, Iwano U.S. Pat. No. 4,954,425, Marsden et al U.S. Pat. No. 4,983,504, Evans et al U.S. Pat. No. 5,246,822, Twist U.S. Pat. No. 5,324,624, Fyson EPO 0 487 616, Tannahill et al WO 90/13059, Marsden et al WO 90/13061, Grimsey et al WO 91/16666, Fyson WO 91/17479, Marsden et al WO 92/01972. Tannahill WO 92/05471, Henson WO 92/07299, Twist WO 93/01524 and WO 93/11460 and Wingender et al German OLS 4,211,460.
Development is followed by bleach-fixing, to remove silver or silver halide, washing and drying.